Sudan's military takes control of oil-rich region

Southern Sudan voted in January to split from the north, but Abyei remains a flash point

Britain's foreign secretary urges all sides to "cease hostilities"

The U.N. has warned that violence jeopardizes relations between the north and south

(CNN) -- Sudan's military has taken control of the disputed oil-rich region of Abyei, the country's foreign ministry said Sunday.

A spokesman for the military wing of the movement that governs Southern Sudan confirmed that Sudan's military controlled the area.

"Abyei has been under attack by the Sudanese armed forces from air and ground," said Sudan People's Liberation Army (SPLA) spokesman Philip Aguer.

Southern Sudan in January voted to split from the north, and is expected to officially become an independent nation in July.

However, the fate of the oil-rich Abyei region remains a flash point.

The Sudanese armed forces said the military in Southern Sudan was behind the attack, but the SPLA denied responsibility.

A statement from U.N. Secretary-General Ban Ki-moon's press office noted that the U.N. compound was shelled by mortar rounds, leaving two peacekeepers injured.

The release, from Ban, also asked for "justice" following earlier attacks May 19 on a U.N.-escorted convoy and on U.N. troops May 10 in Goli. At least 22 people were killed in the more recent attack, which was on Sudanese armed forces and U.N. peacekeepers, according to Sudanese army sources.

"The Secretary-General remains deeply concerned for the safety of the civilian population of the area, the vast majority of whom (have) been forcibly displaced due to the fighting," the U.N. statement said Sunday. "The Secretary-General calls on both parties to immediately cease their military operations, withdraw all forces and armed elements from Abyei and desist from further acts of antagonism."

Sudanese President Omar al-Bashir issued a decree Saturday dissolving Abyei's administration. The area had been governed by representatives from the north and south.

The United Nations said this month that violence in the Abyei region will jeopardize relations between the two sides as they gear up for a permanent separation July 9.

Its peacekeeping mission in Sudan issued a statement Saturday urging "all parties in Abyei to resume dialogue towards reaching a lasting political settlement."

British Foreign Secretary William Hague condemned the recent spike in violence.

"I call on all sides to cease hostilities immediately. All unauthorized forces should be withdrawn from the entire area of Abyei in accordance with past agreements by the parties," he said in a statement Sunday.

In a statement Saturday, the White House called on the Sudanese Armed Forces to stop its offensive in Abyei and withdraw forces.

"Failure to do so could set back the process of normalizing relations between Sudan and the United States and inhibit the international community's ability to move forward on issues critical to Sudan's future," the statement said.

A U.N. Security Council delegation had arrived in Khartoum, Sudan, on Saturday to discuss the ongoing peace process with government officials.